linux-kernel - [PATCH v13 05/35] KVM: PPC: Drop dead code related to KVM_ARCH_WANT_MMU

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Date:   Fri, 27 Oct 2023 11:21:47 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Sean Christopherson <seanjc@...gle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.linux.dev, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Xu Yilun <yilun.xu@...el.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Anish Moorthy <amoorthy@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        "Mickaël Salaün" <mic@...ikod.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH v13 05/35] KVM: PPC: Drop dead code related to KVM_ARCH_WANT_MMU_NOTIFIER

Assert that both KVM_ARCH_WANT_MMU_NOTIFIER and CONFIG_MMU_NOTIFIER are
defined when KVM is enabled, and return '1' unconditionally for the
CONFIG_KVM_BOOK3S_HV_POSSIBLE=n path.  All flavors of PPC support for KVM
select MMU_NOTIFIER, and KVM_ARCH_WANT_MMU_NOTIFIER is unconditionally
defined by arch/powerpc/include/asm/kvm_host.h.

Effectively dropping use of KVM_ARCH_WANT_MMU_NOTIFIER will simplify a
future cleanup to turn KVM_ARCH_WANT_MMU_NOTIFIER into a Kconfig, i.e.
will allow combining all of the

  #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)

checks into a single

  #ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER

without having to worry about PPC's "bare" usage of
KVM_ARCH_WANT_MMU_NOTIFIER.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/powerpc/kvm/powerpc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 7197c8256668..b0a512ede764 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -632,12 +632,13 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		break;
 #endif
 	case KVM_CAP_SYNC_MMU:
+#if !defined(CONFIG_MMU_NOTIFIER) || !defined(KVM_ARCH_WANT_MMU_NOTIFIER)
+		BUILD_BUG();
+#endif
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 		r = hv_enabled;
-#elif defined(KVM_ARCH_WANT_MMU_NOTIFIER)
-		r = 1;
 #else
-		r = 0;
+		r = 1;
 #endif
 		break;
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-- 
2.42.0.820.g83a721a137-goog